Mo-Modified P2-type Manganese Oxide Nanoplates with an Oriented

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Energy, Environmental, and Catalysis Applications

Mo-modified P2-type manganese oxide nanoplates with oriented stacking structure and exposed {010} active facets as long-life sodium-ion battery cathode Quanqing Zhao, Zefeng Guo, Liqin Wang, Yu Wu, Faheem K Butt, Youqi Zhu, Xingyan Xu, Xilan Ma, and Chuanbao Cao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b07950 • Publication Date (Web): 07 Aug 2019 Downloaded from pubs.acs.org on August 7, 2019

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ACS Applied Materials & Interfaces

Mo-modified P2-type manganese oxide nanoplates with oriented stacking structure and exposed {010} active facets as long-life sodium-ion battery cathode Quanqing Zhao,a Zefeng Guo,b Liqin Wang,a Yu Wu,a Faheem K. Butt,c Youqi Zhu,a* Xingyan Xu,a Xilan Ma,a Chuanbao Caoa* a

Research Center of Materials Science, Beijing Key Laboratory of Construction Tailorable

Advanced Functional Materials and Green Applications, Beijing Institute of Technology, Beijing 100081, China b

Datong Coal Mine Group Shuozhou Coal Co.Ltd, Huairen, Shanxi 038300, China

c

Department of Physics, Division of Science and Technology, University of Education

Lahore, Pakistan KEYWORDS: Mo-modification, oxidation state, sodium manganese oxide, nanoplates, sodium-ion battery ABSTRACT. Layered manganese-based cathode materials are of great interest due to their high specific capacities for sodium ion batteries. However, the Jahn-Teller effect and the inevitable phase transition are detrimental for achieving considerable cycling stability and rate capability. Herein, a P2-type manganese oxide nanoplate cathode material modified by Mosubstitution with oriented stacking structure and exposed {010} active facets is reported. The manganese oxide nanoplate cathode yields remarkable capacity retention of 86% after 1200 cycles at 10C (2000 mA g-1). The specific power density is estimated as high as 530 W Kg-1 with a specific discharge capacity 143.9 mA h g-1 at 1C and 89.6% capacity retention up to 100 cycles. The superior electrochemical performances can be attributed to the efficient 1 ACS Paragon Plus Environment

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chemical modification and the unique structural features of the present manganese oxide nanoplate. Mo-modification can endow manganese oxide cathode with enlarged lattice space and average oxidation state and thus favorable Na+ diffusion to inhibit the Jahn-Teller effect and improve the structure stability, thereby achieving an extremely long cycling life. Multilayer oriented stacking nanoplate structure with exposed {010} active facets is also beneficial for providing more surface active sites and shortening the Na+ diffusion path, leading to better rate capability.

1 INTRODUCTION Sodium-ion batteries are emerging as one of the promising next-generation energy storage devices and have attracted extensive research due to high abundance and low cost of sodium resources, as well as their similar electrochemical behaviors to lithium-ion batteries.1-4 Great efforts have been dedicated to exploring various novel cathode, which is of great significance for the development of sodium ion batteries.5 Especially, layered multicomponent sodium transition-metal oxide (NaxTMO2) are considered as the most promising candidates because of simple manipuility, high theoretical capacity and favorable two-dimensional Na+ ions diffusion channel. Recently, P2-type and O3-type NaxTMO2 have captured the research frontier. In particular, P2-type NaxTMO2 have received much more concern due to their lower diffusion barrier, higher ionic conductivity, and smaller hygroscopicity.4,6-10 Considering the abundant resources, low cost and environmental friendliness of manganese, P2-type layered sodium manganese-based cathode has received intensive concern.11,12 However, the Jahnteller distortion induced by Mn3+ ion and the drastic phase transformations caused by larger ionic radius of sodium can cause significantly capacity degradation and poor rate capability during repeated sodium de/intercalation process.13-16 In order to solve the aforementioned problems, heteroatom modification has become an effective strategy, which can not only affect the crystal structure to improve the structural 2 ACS Paragon Plus Environment

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stability at a certain extent and adjust the average oxidation state of Mn to suppress the unstable electronic structure of Mn3+, but also enhance the electronic and ionic conductivities of active materials.17-23 Li and coworkers confirmed that Cu and Mg multi-metal substitution can exhibit synergetic effects in Na0.67Mn0.8Cu0.1Mg0.1O2 cathode material for achieving enhanced structural reversibility.17 Chen et al reported Na0.44Mn0.6Ni0.4-xCuxO2 cathode material doped by inactive copper, which can enlarge lattice space and reduce irreversible reaction resistance to improve cycle performance.8 Despite considerable achievements in heteroatom modification, such as Li,18 Mg,19 Zr,20 Zn,21 etc., the research on effect of Momodification to sodium manganese-based cathode materials are extremely rare.22 In addition, it has been proven that well-structured geometry and surface structure are also extremely advantageous for increasing diffusion dynamics of ions so as to enhance the electrochemical performance in energy storage field.24-35 Theoretically, the P2-type sodium manganese-based cathode materials with hexagonal layered structure promise sodium ion diffusion pathway along parallel to the c-plane. Therefore, in the hexagonal unit cell, the six equivalent sides indexed as {010}, namely (010), (1̅10), (1̅00), (01̅0), (11̅0) and (100) planes, are favorable active planes with open structure for Na+ ions to intercalate. However, there is hardly no report to devote to the surface microstructure engineering of P2-type sodium manganese-based cathode materials with exposed {010} active facets.35 In view of these facts, the desired difunctional synergy combining with advantages of heteroatom modification and structural features enables excellent rate performance and long cycling stability in sodium-ion battery. Herein, we for the first time propose a Mo-modified P2-type manganese-based cathode consisting of multilayer oriented stacking nanoplates with exposing {010} active facets. Mo-modification can increase lattice space and average oxidation state of manganese to facilitate Na+ diffusion and inhibit the Jahn-Teller effect, thereby achieving an extremely long cycle life. Multilayer oriented stacking structure can 3 ACS Paragon Plus Environment


facilitate Na+ diffusion and shorten Na+ diffusion path ， leading to good rate capacity. The obtained Na0.6Mn0.98Mo0.02O2 cathode yields remarkable capacity retention of 86% after 1200 cycles at 10C (2000 mA g-1). The estimated specific power density as high as 530 W Kg-1 is delivered with specific discharge capacity of 143.9 mA h g-1 at 1C (89.6% capacity retention up to 100 cycles). The prominent cycling stability and excellent specific power density of P2type Na0.6Mn0.98Mo0.02O2 with multilayer oriented stacking structure with exposing {010} facets can open a novel avenue to synthesize high-performance sodium manganese-based cathode materials.

2 EXPERIMENTAL SECTION 2.1 Preparation of materials Firstly, the flower-like MnCO3 nanosheets were synthesized by hydrothermal method. Typically, 15 mmol hexamethylenetetramine (HMT) and 10 mmol Mn(Ac)2·4H2O were successively dissolved in 70 ml of ethylene glycol (EG) to form uniform solution under stirring. Then the above solution was added into the stainless steel vessel for 24 h at 180 oC. The obtained precipitate was centrifuged and washed with water and ethanol. After drying for overnight, MnCO3 was pre-sintered for 6 h at 500 oC to convert to Mn2O3. Next, Mo-modified Na0.6Mn(1-x)MoxO2 (x=0, 0.02 and 0.05, donated as NMO, 0.02Mo-NMO and 0.05Mo-NMO) were synthesized. The corresponding stoichiometric ratios of Mn2O3, (NH4)7Mo7·H2O and Na2CO3 were added to a trace amount of deionized water to form a suspension solution for stirring overnight. The mixture was grinded and heated for 3 h at 500 oC and for 12 h at 850 oC.

Finally, the as-synthesized samples were stored in an Ar-filled glove box until used.

2.2 Materials Characterization

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The crystal structures of samples were characterized between 10o and 70o by the X-ray diffraction (XRD) spectroscopy at PANalytical X-pert diffractometer, Netherlands with CuKa radiation. The morphology and microstructure of samples were analyzed by a Hitachi field-emission scanning electron microscope (FESEMS) at Hitachi S-4800 and Transmission electron microscopy (TEM and HRTEM, FEI Tecnai G2 F20, 200 kV). EDS mapping was collected. The valence bond of the surface element was tested using X-ray photoelectron spectroscopy (XPS, PHI Quanteral II, Japan). The composition of the elements in samples was performed through Inductively coupled plasma-atomic emission spectroscopy (ICP-AES, ICAP-6300).

2.3 Electrochemical tests The electrochemical tests were performed through a CR2025 coin cell battery, which was assembled in an Ar-filled glove box. The cathode was composed of active material, super P and polyvinylidene fluoride in a mass ratio of 7:2:1. The mixture was grinded and added to a small amount of NMP to form a uniform suspension. The suspension was coated on an Al foil. After drying overnight at 80oC, it was cut into small discs having a diameter of 14 mm. Metal sodium and glass fibers acted as counter electrodes and separators, respectively. The electrolyte was 1 M NaClO4 dissolved in ethyl carbonate-dimethylcarbonate (EC-DMC, 1:1 v/v) with 5 vol% FEC. The galvanostatic charge and discharge test was performed at CT2001A Land battery testing system. For galvanostatic intermittent titration technique (GITT) tests, the cells were performed at 0.05 C for the second cycle. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out on IM6e electrochemical workstation (Zahner, Germany).

3 RESULTS AND DISCUSSION



As shown in figure 1a, XRD patterns of as-prepared sodium manganese-based cathode are analyzed, where the main diffraction peaks of all samples are well indexed to P2-type hexagonal layered structure (space group: P63/mmc, JCPDS card NO. 27-0751). The diffraction peaks of different Mo-modified materials are mainly attributed to P2-type layered phase, indicating that the modification has no effect on crystal structure. A trace amount of cubic phase Na2MoO4 is observed in 0.02Mo-NMO. As the amount of Mo modification increases, some impurity phases of Na2-xMoO4 appear in 0.05Mo-NMO. Most important, compared with NMO and 0.05Mo-NMO, peak position of 0.02Mo-NMO are left-shifted to lower degrees, as shown in figure 1b, indicating the unit cell expansion, thereby increasing Na+ diffusion. A crystal schematic of the P2 layered structure viewed along b axis and c axis is shown in figure 1c, which consists of alternating stacked edges sharing TMO6 octahedral layers and Na-ion layers. TMO6 octahedral layers and Na ions layers are sequentially stacked in the order of ABA. Rietveld refinement plots of all samples are shown in figure S1. The observed results are consistent with the calculated results, respectively. The corresponding changes in the lattice parameters obtained by Rietveld refinement is displayed in figure 1d. It further confirms that appropriate Mo modification increases the lattice parameter c and unit cell volume to some extent, leading to the improved reaction kinetics of Na+ ions.


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Figure 1. XRD patterns of samples and as insert (a), enlarged (002) diffraction peak (b), crystal schematic of P2-type layered manganese-based structure viewed along b axis and c axis (c), relative changed lattice parameters with different amounts of Mo modification (d). The flower-shaped Mn2O3 microspheres formed by decomposition of MnCO3 are used as precursors to synthesize Mo-modified sodium manganese-based cathode assisted by subsequent solid phase method. Figure S2 and S3 shows the XRD, SEM and TEM of the synthesized Mn2O3 and MnCO3, respectively. The morphological features of Mo-modified sodium manganese-based cathode materials with different Mo contents are performed by SEM and TEM as shown in Figure S4 and S5. Generally, the main morphology presents a plate-like structure, and when the amount of Mo increases to 5%, a small amount of wire-like structure will appear for 0.05Mo-NMO. In figure 2a, more detailed SEM images of asprepared 0.02Mo-NMO sample at high magnification reveal that the plate-like secondary 7 ACS Paragon Plus Environment


particle consists of multilayer oriented stacking nanoplates. Compared with NMO, the modification of the 2% Mo content increases the space between the nanoplates to some extent, which can be beneficial to the infiltration of electrolyte and improve effectively Na+ transportation of, resulting in excellent electrochemical performance. Moreover, the unique structure of multilayer oriented stacking nanoplates is also convenient for increasing the surface reactive sites of electrode material and shortening Na+ diffusion path, leading to excellent rate capability. To get in-depth investigation of the morphology and microstructure, detailed TEM, HRTEM and SAED of 0.02Mo-NMO are performed. The unique structure of multilayer oriented stacking nanoplates is furthermore confirmed in figure 2b. The adjacent lattice fringe space of around 0.247 nm corresponds to the (001) interplanar value of layered structure in figure 2c, which is consistent with the FFT results (insert in figure 2c) and SAED in figure 2d. STEM image and corresponding EDX mapping of figure 2e-i indicate that all elements are uniformly distributed in the stacked nanoplates. In addition, the chemical compositions of sodium manganese-based cathode with different Mo contents are carried out by ICP in Table S1. For NMO and 0.02Mo-NMO, the obtained results are basically consistent with the theoretical values of the experimental design, while the amount of Na is slightly lower for 0.05Mo-NMO.


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Figure 2. SEM image (a), TEM images (b), HRTEM images and FFT as insert (c), SAED image (d), STEM image and corresponding EDX mapping of 0.02Mo-NMO (e-i). The elemental valence characteristics of NMO and 0.02Mo-NMO surface are characterized by XPS. From the survey scan as given in figure S6, the existence of the element Mo 3d is evidenced in 0.02Mo-NMO in addition to the coexisting elements C, O, Mn and Na. XPS curves of Mn2p3/2 of NMO and 0.02Mo-NMO samples before and after cycling are performed in figure 3a and b. Mn 2p3/2 further can be deconvolution into both Mn3+-O bond and Mn4+-O bond.28 The as-prepared both NMO and Mo-NMO samples have an increase in Mn3+ ions after cycling. However, in contrast, the Mo-modified material increased from 51.6% to 59.6%, which is much smaller than bare material increased from 64.9% to 88.62%. These results indicate that Mo modification can improve Mn average oxidation state and provide more robust Mn-O bonds, thereby suppressing the Jahn-Teller distortion induced by trivalent Mn3+ ions and improving the phase stability to be conductive to the capacity retention of materials. In addition, Comparing the changed ratio of Mn3+ before and after cycling, Mo modification only inhibited the production of Mn3+ ions to a certain extent, but Mn3+ ions increased during the charged-discharged process still accelerated Jahn-Teller distortion, resulting in capacity decay. The XPS spectrum of Mo 3d for 0.02Mo-NMO is provided in figure S7, which has two strongest peaks at 232.3 eV and 235.4 eV. Many literatures about the fitting spectrum of Mo 3d suggest that the binding energy of Mo6+ 3d3/2 is higher than 234 eV.36,37 The binding energy of Mo4+ 3d3/2 and Mo6+ 3d5/2 locates between 230 and 234 eV. In addition, these results are also consistent with XRD analysis. Owing to the smaller radii of Mn4+ (0.53 Å) and Mo6+ (0.62 Å) than Mn3+ (0.645 Å), the (002) peak of 0.02Mo-NMO shifts to a lower degree.



Figure 3. XPS curves of Mn2p3/2 of NMO (a) and 0.02Mo-NMO (b) samples before and after cycling. The Na storage performance of the Mo-modified NMO cathode materials is evaluated by galvanostatic charge-discharge tests between voltage range of 2 to 4 V at different rate (1 C = 200 mA g-1). Figure S8 displays the 2nd charge-discharge profiles of NMO, 0.02Mo-NMO and 0.05Mo-NMO at 0.2 C that match with the CV curves of them at a scan rate of 0.1 mV s-1 in figure S9. The similar electrochemical behavior of Mo-modified NMO cathode can be attributed the typical NaxMnO2 layered cathode, showing multiple plateaus below 4 V, which is mainly due to Na+/vacancy superstructures formed by the electrostatic interactions of NaNa and Na-Mn during the sodium de/intercalation.38 The most conspicuous redox couples at ca. 2.3V mainly are due to the redox reactions of Mn3+/Mn4+. In addition, it can be concluded from the voltage profiles that 0.02Mo-NMO cathode exhibits a higher discharge voltage platform, correspondingly improving the specific energy density. In order to further evaluate the high current performance, the cells are tested for charge and discharge at different rates between 0.2C and 10C in figure 4a. 0.02Mo-NMO shows the best rate capability and capacity 10 ACS Paragon Plus Environment

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retention, which yield the discharge capacity of 166.8 mA h g-1 at 0.2C. Even at such a high current density of 10 C (2 A g-1), the discharge capacity of 77.5 mA h g-1 is delivered for 0.02Mo-NMO, much higher than NMO (57.1 mA h g-1) and 0.05Mo-NMO (52.1 mA h g-1). Furthermore, compared with NMO in figure S10, the corresponding voltage curves of 0.02Mo-NMO at various rates indicate only the slight increase in the voltage polarization, as shown in figure 4b. When the cells are charged-discharged at 1C, 0.02Mo-NMO obtains the most outstanding cycle stability with the capacity retention of 89.6%, whereas the capacity retention of NMO and 0.05Mo-NMO are 82.4% and 76.2% (figure 4c), respectively. Figure 4d provides a corresponding voltage curves for 0.02Mo-NMO at 5th, 10th, 20th, 50th and 100th at 1C, with slight voltage polarization during continuous deep cycles. Surprisingly, as displayed in figure S11, the second discharge capacity of 0.02Mo-NMO are 143.9 mA h g-1, higher than that of NMO (131.6 mA h g-1). In view of the higher specific discharge capacity, the obtained specific energy density and specific power density of 0.02Mo-NMO reaches to 390 Wh Kg-1 and 530 W Kg-1 at 1C. Most importantly, in figure 4e, the 0.02Mo-NMO cathode delivers the surprising capacity retention of 86% and very stable coulombic efficiency at high current density of 10C (2000 mA g-1). So far, compared with the relevant literature reported in terms of energy and cycle stability, 0.02Mo-NMO cathode exhibits highlevel performances, as shown in table S2.



Figure 4. Rate capability of NMO, 0.02Mo-NMO and 0.05Mo-NMO from 0.2 C to 10 C (a), voltage plots of 0.02Mo-NMO at different rates (b), cycling performances of NMO, 0.02MoNMO and 0.05Mo-NMO at 1C (c), the corresponding galvanostatic charge-discharge plots in 5th, 10th, 20th, 50th and 100th at 1C (d), cycling performances and columbic efficiency at 10 C (e) of 0.02Mo-NMO.


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To insight into Mo-modification effects and Na+ diffusion coefficient of electrode interface, EIS of fresh samples are measured before cycling. In figure 5a, Re, Rf and Rct at high frequency region represent resistances of electrolyte, solid electrolyte interface film and charge transfer, respectively. And the Na+ diffusion process in the solid phase of electrode can be obtained in slope line in the low frequency region. The sodium ion diffusion coefficient (DNa+) of electrode can be calculated according to the following equation: DNa+ =

(1)

Where R, T, A, n, F and C are the gas constant, absolute temperature, surface area of the electrode, number of electrons per molecule during oxidization, Faraday constant and concentration of sodium ions. Visibly, the sodium ion diffusion coefficient (DNa+) is related to Warburg coefficients (σ), which belong to the slopes obtained the relationship between Z’ and ω-1/2 at low frequency region in figure 5b. Therefore, the DNa+ of 0.02Mo-NMO is highest than that of NMO and 0.05Mo-NMO because 0.02Mo-NMO has the smallest σ. Obviously, the sodium ions diffusion of 0.02Mo-NMO is faster than that of NMO and 0.05Mo-NMO. Moreover, compared with bare materials, there is a remarkable smaller in total resistance for 0.02Mo-NMO before and after cycling in figure S12. It demonstrates that Mo modification can effectively improve the conductivity of the materials, which is consistent with the improvements of rate capability and cycling stability. And the impedance parameters of NMO, 0.02Mo-NMO and 0.05Mo-NMO before and after cycling can be summarized in table S3 and S4. GITT is also a reliable method for calculate the Na+ chemical kinetics diffusion coefficient. The GITT curve of 0.02Mo-NMO at 0.05 C for the second cycle is performed in figure 5c and d (the GITT test of NMO is shown in figure S13). The sodium ion diffusion coefficient (DNa+) of electrode can be obtained according to the following equation:



DNa+ =

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(2)

Where nm is the number of molar, Vm is the molar volume of electrode, A is the area of electrode. Therefore, DNa+ can be obtained by setting each diffusion voltage relaxation curve. DNa+ of NMO and 0.02Mo-NMO under different charges states is shown in Figure 5d. Obviously, the average value of DNa+ of 0.02Mo-NMO is around 2.67 × 10-10 cm2 s-1, higher than that of NMO (1.62 × 10-10 cm2 s-1) during the entire charging process, indicating the excellent rate capability and cycling stability. In addition, Na+ apparent diffusion coefficient is evaluated by CV curves at different scan rates and corresponding linear fitting of peak current versus square root of the scan rate of all samples, as shown in figure 6. According to the Randles-Sevcik equation, as-prepared 0.02Mo-NMO exhibits excellent kinetics upon Na+ deintercalation/intercalation. All these results indicate that Mo modification can simultaneously improve the conductivity and Na+ ion reaction kinetics of materials, resulting in good cycle stability and rate capability.


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Figure 5. EIS and equivalent circuit (a), the relationship plots between Z’ and ω-1/2 at low frequency region (b) of samples. GITT curve (c) and the corresponding DNa+ (d) of 0.02MoNMO

Figure 6. CV curves at different scan rates and corresponding linear fitting of peak current versus square root of the scan rate for NMO (a and b), 0.02Mo-NMO (c and d) and 0.05MoNMO (e and f) samples.



To better assess the impact of Mo modification on material structure, ex-situ XRD detailedly discusses the phase transition of 0.02Mo-NMO during different charged-discharged states at 2nd cycle, as shown in figure 7a, b and c. Obviously, there is hardly change for the XRD patterns of 0.02Mo-NMO except for the diffraction peaks substrate Al. Furthermore, The enlarged (002) peak between 14º and 17º slightly shift to a small angle consistent with the reports in the literature, caused by an increase in electrostatic repulsion between adjacent O atoms during sodium de/intercalation.39-41 Meanwhile, when discharged to 2V again at 2nd cycle, the (002) peak still recovers to the original position obtained from discharging to 2V at 1st cycle. These results can confirm that Mo modification causes the unit cell expansion and enhances structural reversibility during sodium de/intercalation, which is beneficial to the cycle stability and rate capability. In addition, as shown in figure S14, the main diffraction peaks of 0.02Mo-NMO are still well ascribed to initial structure without phase transformations up to 100 cycles, indicating that the structure reversibility is favorable for achieving excellent long cycling performance.

Figure 7. The voltage plot (a) and the corresponding Ex situ XRD pattern (b) of 0.02MoNMO at different charged-discharged states for 2nd cycle, the enlarged (002) peak of ex situ XRD pattern of 0.02Mo-NMO between 14º and 17º (c). 16 ACS Paragon Plus Environment

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Furthermore, SEM, TEM and HRTEM of 0.02Mo-NMO after 100 charge-charged cycles are also performed to insight into the microstructure and morphology. SEM image (figure 8a) and TEM image (figure 8b) can clearly point out that the unique structure of multilayer oriented stacking nanoplates can be still remained, which is advantageous for increasing the surface reactive sites of the material and shortening the Na+ diffusion path, leading to excellent long cycle performance. Importantly, the space between nanoplates becomes larger with the repeatedly sodium de/intercalation, which increases the Na+ diffusion, leading to excellent rate capability. In addition, the adjacent lattice fringe space of around 0.247 nm corresponds to the (001) interplanar value of the layered structure in figure 8c, which is consistent with the FFT results.

Figure 8. SEM image (a), TEM image (b) and HRTEM image (c) of 0.02Mo-NMO after 100 cycles at 1C.

4 CONCLUSION In summary, a P2-type Na0.6Mn0.98Mo0.02O2 cathode with multilayer oriented stacking nanoplates by exposing {010} facets is successfully designed via combining structural features with the other atom modification. Benefitting from the dual-function synergy, on the one hand, the electrode can not only be quite favorable for the infiltration of the electrolyte and the transportation of Na+, but increase the surface reactive sites of the material to improve the capacity; On the other hand, Mo-modification can improve the lattice space, the average 17 ACS Paragon Plus Environment


oxidation state of Mn and structure stability, suppressing the Jahn-Teller distortion caused by trivalent Mn3+ ions and the drastic phase transformations, which is very effective in enhancing the capacity retention. As a result, the P2-type Na0.6Mn0.98Mo0.02O2 cathode yields remarkable capacity retention of 86% after 1200 cycles at 10C (2000 mA g-1). The estimated specific power density as high as 530 W Kg-1 is delivered with a specific discharge capacity of 143.9 mA h g-1 at 1C (capacity retention 89.6% up to 100 cycles). These values indicate that Momodification with multilayer oriented stacking nanoplates by exposing {010} facets is a prospective approach to enable sodium manganese-based cathode with excellent cycling performances. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. XRD, SEM and TEM images of precursors. SEM images of NMO, 0.02Mo-NMO and 0.05Mo-NMO. The survey scans of NMO and 0.02Mo-NMO. The 2nd galvanostatic chargedischarge plots at 0.2 C. The second CV curves of NMO, 0.02Mo-NMO and 0.05Mo-NMO at a scan rate of 0.1 mV s-1. Voltage plots of NMO at different rates. The second galvanostatic charge/discharge curves versus specific capacity and specific energy density of NMO and 0.02Mo-NMO. The cycling performance of 0.02Mo-NMO after 200 cycles at 1C. XRD patterns of 0.02Mo-NMO before the cycle and after 100 cycles. The GITT curve and the corresponding DNa+ of NMO. ICP results of Mo-modified P2-type sodium manganese-based cathode. Comparison electrochemical performance with other cathode materials. Impedance parameters of the Mo-modified NMO electrodes. AUTHOR INFORMATION Corresponding Author 18 ACS Paragon Plus Environment

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*E-mail: [email protected](Y. Zhu) *E-mail: [email protected](C. Cao) ORCID: Youqi Zhu: 0000-0003-0184-729X Chuanbao Cao: 0000-0003-2830-4383 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (No. 21371023) and Beijing Institute of Technology Research Fund Program for Young Scholars (3090012221914). REFERENCES (1) Kim, H.; Kim, H.; Ding, Z.; Lee, M. H.; Lim, K.; Yoon, G.; Kang, K. Recent Progress in Electrode Materials for Sodium‐Ion Batteries. Adv. Energy Mater. 2016, 6, 1600943. (2) Guo, S.; Yi, J.; Sun, Y. and Zhou, H. Recent Advances in Titanium-Based Electrode Materials for Stationary Sodium-Ion Batteries. Energy Environ. Sci. 2016, 9, 2978-3006. (3) Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research Development on SodiumIon Batteries. Chem. Rev. 2014, 114, 11636-11682. (4) Yao, H.-R.; Wang, P.-F.; Gong, Y.; Zhang, J.; Yu, X.; Gu, L.; OuYang, C.; Yin, Y.-X.; Hu, E.; Yang, X.-Q.; Stavitski, E.; Guo, Y.-G. and Wan, L.-J. Designing Air-Stable O3-type Cathode Materials by Combined Structure Modulation for Na-Ion Batteries. J. Am. Chem. Soc. 2017, 139, 8440-8443. 19 ACS Paragon Plus Environment


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Mo-Modified P2-type Manganese Oxide Nanoplates with an Oriented

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